Visually impairing cataract, or clouding of the lens, is the leading cause of preventable blindness in the world. Presently, cataracts are treated by surgical removal of the affected lens and replacement with an artificial intraocular lens (“IOL”). Cataract extractions are among the most commonly performed operations in the world.
FIG. 1 is a diagram of an eye 10 showing some of the anatomical structures related to the surgical removal of cataracts and the implantation of IOLs. The eye 10 comprises an opacified lens 12, an optically clear cornea 14, and an iris 16. A lens capsule 18, located behind the iris 16 of the eye 10, contains the opacified lens 12, which is seated between an anterior capsule segment or anterior capsule 20 and a posterior capsular segment or posterior capsule 22. The anterior capsule 20 and the posterior capsule 22 meet at an equatorial region of the lens capsule 18. The eye 10 also comprises an anterior chamber 24 located in front of the iris 16 and a posterior chamber 26 located between the iris 16 and the lens capsule 18.
A common technique of cataract surgery is extracapsular cataract extraction (“ECCE”), which involves the creation of an incision near the outer edge of the cornea 14 and an opening in the anterior capsule 20 (i.e., an anterior capsulotomy) through which the opacified lens 12 is removed. The lens 12 can be removed by various known methods including phacoemulsification, in which ultrasonic energy is applied to the lens to break it into small pieces that are promptly aspirated from the lens capsule 18. Thus, with the exception of the portion of the anterior capsule 20 that is removed in order to gain access to the lens 12, the lens capsule 18 remains substantially intact throughout an ECCE. The intact posterior capsule 22 provides a support for the IOL and acts as a barrier to the vitreous humor within the posterior chamber 26. Following removal of the opacified lens 12, an artificial IOL is typically implanted within the lens capsule 18 through the opening in the anterior capsule 20 to mimic the transparency and refractive function of a healthy lens. Alternatively, a lens material may be injected to fill the lens capsule 18 and create an artificial “lens” in situ. The IOL may be acted on by the zonular forces exerted by a ciliary body 28 surrounding the periphery of the lens capsule 18. The ciliary body 28 anchors the IOL in place and facilitates accommodation, the process by which the eye 10 changes optical power to maintain a clear focus on an image as its distance varies.
A frequent complication of ECCE and other forms of cataract surgery is opacification of the posterior capsule 22. Posterior capsule opacification (“PCO”) results from the migration of residual lens epithelial cells from the “equatorial” region of the lens toward the center of the posterior capsule 22. Subsequent to ECCE, the lens epithelial cells may proliferate between the IOL and the surface of the posterior capsule 22, leading to wrinkling and clouding of the normally clear posterior capsule 22. If clouding of the posterior lens capsule 22 occurs within the visual axis, then the patient will experience a decrease in visual acuity and may require additional surgery to correct the patient's vision.
A widely utilized procedure to clear the visual axis of PCO is Neodymium:Yttrium-Aluminum-Garnet (“Nd:YAG”) laser capsulotomy, in which a laser beam is used to create an opening in the center of the cloudy posterior capsule. However, Nd:YAG laser capsulotomy exposes patients to the risk of severe complications that can lead to significant visual impairment or loss, such as retinal detachment, papillary block glaucoma, iris hemorrhage, uveitis/vitritis, and cystoid macula edema. Moreover, the laser energy is ordinarily directed though the IOL, which may damage the optics of the implant or disrupt its placement within the lens capsule. Also, a laser capsulotomy may compromise the accommodative ability of the lens implant. Accordingly, there exists a need to prevent the occurrence of PCO rather than treating PCO at a later date after implantation of an IOL. This is especially desirable for the new generation of IOLs (i.e., accommodating IOLs) that are capable of accommodating in response to ciliary body contraction and need an intact posterior capsule to optimally function.
Other attempts to prevent PCO have included constructing IOLs to include sharp posterior edges to provide a structural barrier to the migration of lens epithelial cells from the equatorial zone to the visual axis of the posterior capsule 22. However, such lenses are relatively expensive and may introduce complications of their own, such as capsular adhesions. Still other attempts to prevent PCO have included the introduction of various chemical agents into the lens capsule 18 to destroy the residual lens epithelial cells before they migrate between the IOL and the posterior capsule. However, the use of these agents has been limited by their cytotoxic effects on other cells within the eye.
There remains a need for a device, system, and method to reduce the need for PCO treatments and their associated costs by reducing the chance of PCO before implantation of an artificial IOL. The system and methods disclosed herein overcome one or more of the deficiencies of the prior art.